Communication systems are available which provide service over a wide area, such as nationwide or even globally. Such wide area systems are made up of numerous local area systems which provide service to a particular geographic area, such as a city or region encompassing a group of cities. Such wide area systems often operate on numerous radio communication frequencies and require that a communication receiver that is allowed to roam between the local area systems be capable of scanning the numerous frequencies in order to identify one or more frequencies designated to carry messages directed to the communication receiver.
Depending upon the grade of service required by a subscriber, the communication receiver carried by the subscriber will be assigned to a home system which provides coverage within the local geographic area, or region, in which the subscriber is predominantly located, and will be assigned one or more addresses to enable message delivery from a variety of sources. In some instances, the messages which are being delivered are directed to a group of subscribers, in which case the communication receiver will be assigned a group address.
Early wide area communication systems required the addresses which are assigned to the communication receivers to be coordinated, which, depending upon the signaling protocol utilized to deliver the messages greatly limited the number of subscribers which could roam from one region to another.
The address limitation was improved in another prior art wide area communication system, by appending a system ID to each individual address assigned to the communication receiver, thereby creating a number of long addresses which corresponded one for one to the number of individual addresses assigned to each communication receiver. In this system, addresses assigned locally could be reassigned to other communication receivers operating locally in other geographic areas. The long addresses had to be transmitted in batches independent of the regular addresses in order to prevent false address detection by another local area communication receiver.
With the advent of higher speed paging protocols, it is apparent that the paging user is expecting to receive more information services and other group messages in addition to traditional personal paging services. As regional and global roaming become commonplace, the paging user will expect the services available in his local coverage area to be forwarded to him as he roams. This increasing traffic per user and the growth of roaming services in general will result in the service provider focusing the roaming traffic into only the coverage areas requested by the traveler thus maximizing the channel capacity of the total roaming infrastructure. Focused roaming complicates the networking aspects of the infrastructure over the past tendency to send roaming traffic into areas much larger than the actual coverage required by the roaming subscriber. It also complicates the pager operation especially in the areas between two coverage areas where the pager does not know which signal is carrying its traffic.
Thus, what is needed is a method and apparatus that provides flexible roaming capability to a receiving device operating within a radio communication systems.